A number of processes are currently being used commercially for converting fossil fuels to electricity. These principally include the cycle power plant incorporating the Brayton and Rankine cycles. A third cycle, namely the Kalina cycle is just now being commercialized.
The Brayton cycle is the process used in gas turbines. In the Brayton cycle, air is compressed in a compressor, and then combusted with fuel, to generate high temperature and high pressure gases which are then expanded through a turbine. Work extracted from the hot gases in the turbine is used to drive a generator for the production of electricity. The combustion process results in the formation of carbon dioxide, water and nitrogen oxides, all of which are released in an uncontrolled fashion to the environment.
The Rankine cycle is commonly known as the steam cycle. In the Rankine cycle, water is boiled at high temperature and pressure. The resulting steam is then expanded to a turbine, extracting work to drive an electric generator. The heat is then removed from the steam in a condenser, converting it to liquid water which is then pumped to higher pressure and returned to the boiler. A combined cycle power plant uses the high temperature exhaust gases in the Brayton cycle as a source of heat in the Rankine cycle.
In the Kalina cycle, heat is added to a multi-component mixture that typically contains ammonia and water. This causes the most volatile component to boil off at the lowest temperature. The boiling point changes with the composition, allowing the boiling process to occur at a range of temperatures. This is unlike the Rankine cycle where the boiling temperature is uniquely determined by the pressure. The vapor produced in the boiling process then passes through a turbine which drives the generator, and then to an absorber. The low volatile liquids (which are not boiled in the boiler) are returned to the absorber where they absorb the vapor exhausted from the turbine. The resulting solution is then pumped to a higher pressure and returned to the boiler. The Kalina process is described in U.S. Pat. Nos. 4,346,561 and 4,489,563. A combined cycle where the Kalina cycle replaces the Rankine cycle used in conventional combined cycle plant is currently under development.
U.S. Pat. No. 4,099,575 describes the use of a absorption/regeneration power cycle for driving a gas turbine, and also for producing cooling in the conventional refrigeration cycle. The process uses potassium bicarbonate and potassium carbonate as the regeneration and absorption fluids. The process was described for use in a desaltination plant to produce water from sea water, which, in combination with such a plant, can also be used to generate electrical power. There is no teaching or suggestion in U.S. Pat. No. 4,099,575 of using the absorption/regeneration cycle in combination with any other power cycles known in the art.